US2014/0351509A discloses a system capable of taking advantage of the operation speed of a relatively high-speed interface to the outside while internally using a relatively low-speed interface. Specifically, the system is connected to a host through a Universal Serial Bus (USB) 3.1 interface which is a relatively high-speed interface. In the system, RAID 0 is configured by a plurality of Solid State Drives (SSDs) which are connected with one another through a plurality of relatively low-speed serial ATAs (SATAs), and data which the host has requested the system to store is divided into blocks and is written in two independent SSDs by performing a striping process.
In the above-described system, in some cases such as a case of configuring SSDs in RAID 5 or 6 in order to secure redundancy, when it is intended to further extend the system, storages configured in RAID 5 or 6 are required, instead of SSDs, and therefore, the system scale excessively increases. That is, in the related-art system, when it is intended to extend the system in order to secure redundancy, the system scale would excessively increase.